TOPIC: Oxygen free Copper V 110ETP

We roll copper into rectangular wire. We use ETP 110 but our customer is asking for OF 102 (cast & rolled). Does anybody know what the advantages/disadvantages are for each type with regard to suitability for rolling and quality of wire produced?

This is a wire and cable forum and this particular section is for the most part focused towards the electrical industry. Saying that, we think we need to clarify the ETP grade of copper you are using for your products since copper 110 is typically used in Welding fixtures, anodes, bus bar in electrical power installations, ground straps, automotive rectifiers, some conductors, glass-to-metal seals, high resistance-ratio cryogenic shunts, lead-in wire seals, transistor component bases, bus conductors, wave guides, hollow conductors, anodes for vacuum tubes, and microwave tubes. This grade only contains 99.9% copper.

We wonder if you are using ETP C11000 since this is the most popular form of pure copper and is the standard electrical wire grade of copper (C11000). This grade contains 99.95% Cu, 0.03% O2, and less than 50 ppm metallic impurities. It has a high electrical conductivity, in excess of 100% IACS. In the as cast form it is called electrolytic tough pitch (ETP) copper.

From the WAI Nonferrous Wire Handbook Volume 3: Principles and Practice: "Oxygen-free copper (less than 10 ppm of oxygen) is not the preferred choice for the magnet wire industry because it has a higher annealing temperature than ETP". That statement however probably relates more to enameling than anything else.

Another excerpt is " Oxygen free coppers (OF) are used whenever extensive amounts of cold work are needed or when the wire is exposed to a hydrogen atmosphere at elevated temperatures, thereby increasing the susceptibility to hydrogen enbrittlement." My own experience with deeply corrugated, longitudinally applied, 10 mil copper shielding tape certainly bore this out. (ETP corrugated copper tape would crack from cold work when the cable was flexed.)

There are 6 references for oxygen-free copper in Volume 3. It is available here if it is not already in your company's technical library: www.wirenet.org/waistore/productdetail.cfm?productid=12 In the "Physical Metallurgy" chapter, there is much technical detail (Almost 9 pages) and many graphs relating to the effect of oxygen content on copper. We certainly cannot reproduce all of this copyrighted information here.

Finally, there was a paper presented at WAI's 76th Annual Convention (Wire Expo) in Boston, May, 2006 and published in Wire Journal International in September 2007. It was titled "Metallurgical and wiredrawing performance comparison of ETP and oxygen-free copper".

The description states: "The differences in manufacturing ETP and oxygen-free copper products are reflected in their metallurgical and physical characteristics, which ultimately defines their performance and suitability for different wire and cable products. ETP rod manufacturing involves casting in a metallic mold followed by hot rolling stages. In contrast, oxygen-free products utilize casting in a graphite mold, which may be followed by cold rolling. The distinctive differences include copper matrix non-uniformities and inclusions."